1. Field of the Invention
The present invention relates generally to a removable crank for applying manual power to a rotary device, such as a marine winch, and is more particularly concerned with a crank of the foregoing type and having improved locking means for securing same to the rotary device.
One type of manually powered rotary device to which the present invention is directed is a marine winch for drawing in or releasing, for example, lines, sheets and ropes on sailboats or, in the case of fishing or cargo boats, for hauling and/or lifting various diverse loads such as traps, nets and cargo. Marine winches broadly consist of a drum rotatably mounted on a base secured, for example, to the deck or rail of the boat. A removable crank handle is used to turn the drum, or in the case of a winch equipped with a reduction gear train, to turn the input drive shaft thereto.
The cranks utilized are preferably removable from the winch in order to facilitate removal of the rope or line, cleaning, storage and/or repositioning of the crank to overcome mechanical or physical deadspots in the rotation cycle. Such hand cranks are also desirably removable for purposes of passenger and crew safety and in order to avoid interference with the movement of the crew.
Another type of manually powered rotary device with which such removable cranks are commonly utilized are throttle controls for auxiliary engines in sailboats. Such controls are generally mounted in the cockpit or cabin of the craft and, when auxiliary power is not in service, such as when the boat is under sail, the crank is desirably removed from the throttle control and stowed for purposes of passenger and crew safety.
Yet other types of manually powered rotary devices susceptible of use of removable cranks therewith are various land based manually powered winches such as boat trailer winches, gin pole hoisting apparatuses, automotive winches and the like. Here, the provision of removable cranks for such devices provides the device with a convenient means for disabling same when not in use, thereby preventing, or at least mitigating, against unauthorized handling and/or vandalizing thereof.
As will be appreciated, while use of removable cranks in association with manually powered rotary devices of the foregoing types is certainly highly desirable, it is obviously essential that the removable crank utilized for such applications comprise suitable means by which the crank may be securely locked into its operating engagement with the rotary device. This is so because winch operations often involve heavy imposed loads during which, if the driving connection between crank and winch is inadvertently lost, catastrophic results may ensue. Such locking security is also essential in auxiliary power throttle operations because sailboat auxiliary power is often used for purposes of precisely navigating the boat in critically close quarters such as in harbors, narrowly marked channels, estuaries and the like. Under these conditions the loss of throttle control due to accidental dislodgement of the crank from the throttle, even if only temporary in nature, can obviously lead to substantial adverse results.
2. Description of the Prior Art
Removable cranks generally comprise an elongate lever or moment arm having a handle rotatably secured to one end thereof for manipulation by the user and an extension fixed to the other end thereof, said extension extending in a direction opposite the direction of the handle. Typically, the extension is keyed and mates with a cooperatively keyed socket in the power receiving element of the manually powered rotary device. A particularly desirable keying or spline geometry for the crank extension is known as the double square, i.e., the extension, taken in cross section, has the geometry of two superimposed squares rotated 45.degree. with respect to one another. This type of cross sectional geometry of the crank extension is well illustrated in, for example, U.S. Pat. No. 3,962,935, to Hutton et al.; and U.S. Pat. No. 4,225,118, to Ottemann. The common method of locking the crank in place is to provide a single square plate rotatably mounted below the free end of the keyed extension, said plate being rotatably operable by means of a knob attached to a shaft housed within the longitudinal axis of the extension. When the plate is aligned with one or the other of the squares of the extension the handle may be inserted or removed from its receiving socket. When the square plate is rotated from this aligned condition the corners of the square instead align with one set of the splines or keys of the socket to prevent removal therefrom.
Referring to FIG. 1 hereof, there is shown in perspective an illustration of the prior art removable crank mechanism as known to the present applicant and as applied to a sailboat winch representing the manually powered rotary device. Winch drum 10 is rotatably mounted on base 12 and comprises a keyed socket 14 for receiving mutually keyed crank extension 16 affixed to one end of crank lever arm 18. A handle 17 for gripping and manipulation of the crank by the operator is journalled to the other end of the crank lever arm 18 and extends in a direction opposite that of the crank extension 16. Retaining plate 20, shown at an exaggerated distance from the lower surface of extension 16, is fixedly secured to rotatable shaft 22. Shaft 22 is rotatably housed within the axis of the extension 16 and is affixed at its upper end to knob 24, also shown at an exaggerated distance from the upper surface of the lever arm 18.
Socket 14 and extension 16 are each correspondingly formed in the above described geometry of the double square, thereby providing the extension 16 with a plurality of driving surfaces 16(a) which mate and cooperate with the corresponding driven surfaces 14(a) of socket 14. Plate 20 is exactly in the cross sectional dimensions of one of the squares of the crank extension 16. Thus, when the plate 20 is aligned with one of the sets of the squares of the crank extension 16, said extension will fit the socket and be engageable therewith. Once so engaged the plate 20 is rotated approximately 22.5.degree. by means of knob 24, thereby to cause the corners thereof to underlie the keys or splines of the socket 14 and to thereby prevent disengagement and withdrawal of the crank extension 16 from the power receiving socket 14. When removal of the crank is desired, the knob 24 is manipulated to bring the plate 20 back into alignment with one of the sets of the squares of the crank extension 16, thereby freeing the extension 16 for removal from the socket 14.
The holding or locking forces in the removable crank of the prior art are thus borne mainly by the corners of the square plate 20 and its point of attachment to the shaft 22. In practice, the rough handling often imposed upon such cranks, particularly in winch operations, leads to the quick destruction of the plate 20 by fracture thereof, by peening of its corners and/or by disengagement of the plate from its fixation to the rotatable shaft 22. Too, by its positioning at the end of the crank extension 16, when the crank is removed from the socket 14 the sharp exposed multiple corners of the plate 20 can often be damaged by accidental impact with hard exterior surfaces, or can themselves do injury to other object surfaces or personnel if the removed crank is improperly stowed, acidentally dropped or otherwise inartfully handled.
The present invention presents an alternative approach to securing a removable crank into the receiving cooperative socket of a manually powered rotary device by providing the crank extension with a retractable elongate locking element slideably housed therein. Means are provided by which the free end of the retractable locking element can be extended to a locking condition and retracted to a removal condition, said free end, when in the extended locking condition of the locking element, engaging a cooperative circumferential groove disposed in the receiving socket. Manual control of retraction of the locking element from its locking engagement with the circumferential groove is achieved by means located exterior of the extension. Desirably, the locking element of the crank of the present invention is disposed at a substantial angle relative to the transverse plane of the extension. The locking element of the crank, when the crank extension is received in the socket of a manually driven rotary device and said element is in the extended locking condition, permits the crank extension to rock or cock into a slightly off axis condition relative to the receiving socket under the manual forces applied at the handle end of the crank. Such cocking of the extension relative to the socket causes the driven surfaces of the socket and the driving surfaces of the extension to wedge beneficially together throughout substantially the entire rotation cycle of the crank while avoiding the imposition of injurious stresses upon the locking element.
As will be better understood from the following description the removable crank of the present invention provides for rapidity, security and ease of engagement and disengagemnt thereof to and from the receiving socket of a manually powered rotary device while exhibiting greatly improved service life relative to the prior art discussed above. In addition, the crank of the present invention, when removed from the manually powered rotary device employing same, avoids presentation of multiple sharp and potentially injurious corners to the environment.
Other objects and advantages of the present invention will, in part, appear hereinafter and will, in part, be obvious.